Method of producing lead alloys



Patented June 2, 1936 UNITED STATES PATENT OFFICE 2,042,625 METHOD OFPRODUCING LEAD ALLOYS No Drawing. Application October 28, 1933,

Serial No. 695,665

11 Claims.

This invention relates to alloys and has for an object the provision ofan improved method of making lead base alloys. More particularly, theinvention contemplates the provision of an improved method of producingalloys comprising lead and copper.

Lead base alloys containing copper possess desirable properties andcharacteristics not possessed by similar substantially copper-freeproducts. Thus, for example, an alloy consisting essentially of lead andan amount of copper up to about .06% of the weight of the lead possesseshigher tensile and compression strength, has a finer crystal size and ismore resistant to certain types of corrosion than ordinary copper-freerefined lead, while at the same time, it retains the softness,workability, and other properties characteristic of refined lead. Thefollowing table shows the relative tensile strength of such an alloy:

Ult. tensile Type of lead strength Lbs. per sq. in.

Very pure lead 1600 to 1650 Desilvered refined lead 1750 to 1835 Copperbearing lead 2300 to 2370 This type of alloy is particularly desirablefor use in lead cable sheathing and for chemical plant construction.

Copper is almost always 'present in unrefined lead bullion, but it isfrequently removed in the refining process. In the refining of leadbullion by the Parkes process, silver-is removed therefrom by theaddition of metallic zinc. Copper, if present in the lead bullion, isalso removed by the zinc in this operation. Therefore, all lead bullionwhich carries values in silver and which is refined by the Parkesprocess produces a refined lead which is practically free from copper.On the other hand, lead produced from silverfree bullion which is notdesilverized usually retains from .04 to .06% copper.

The amount of copper which is required to impart the above-mentionedbeneficial properties to lead is very small and corresponds to theeutectic or solubility of copper in refined lead at its freezing pointwhich, for all practical purposes, is .06% Cu. Concentrations of copperin excess of this amount usually add nothing to the advantages obtainedat the eutectic composition. Also, there is no advantage derived fromthe addition of copper to lead unless the copper is uniformlydistributed throughout the mass of lead.

It is difiicult to obtain high-grade alloys comprising copper and leadby mixing together and heating metallic copper and metallic lead because5 of the high melting point of copper and the low solubility of copperin lead. The alloys formed by this method are invariably spotty, ofuncertain compositions, and the properties of such alloys are,therefore, necessarily doubtful.

The present invention provides a method by means of which alloyscomprising copper and lead in which the copper is uniformly distributedmay be produced at reasonably low temperatures. The method of theinvention involves the treat- 15 nient of a molten bath containingmetallic lead and a copper compound under such conditions as to effectreduction of the copper compound and dispersion of the resultingmetallic copper throughout the molten bath.

According to a. preferred method of the invention, copper is caused tochemically precipitate in a molten bath containing metallic lead bycontacting the material of the bath with a reagent composed of chemicalequivalent amounts 25 of copper and chlorine. In its simplest form, thereagent consists of cuprous or cupric chloride, but, in its commercialapplication, the reagent may comprise a mixture of one or more othersalts of copper with one or more other metal chlorides such, forexample, as alkali and alkaline earth metal chlorides in which thecopper salts and chlorides are present in such proportions as to providechemically equivalent amounts of copper and chlorine. A suitable reagentmixture may comprise, for example, equivalent amounts of coppersulphate, CUSO4'5H2O and sodium chloride, NaCl, in. which case the tworeact to form the active ingredient CuC12-2H2O and the inactiveingredient NazSO4. If molten metallic lead is allowed to come in contactwith any of such reagents at about 900 F. the lead reacts ultimatelywith copper chloride to form lead chloride and metallic copper accordingto the following equation:

The following examples of methods of the invention are given forpurposes of illustration and in order to provide a more completedisclosure of the invention, and it is to be understood that theinvention is not to be limited by the specific procedures herein setforth.

Following is a description of a simple procedure for producing an alloycontaining copper and lead in accordance with the method of theinvention:

Lead is melted down in an iron kettle and the temperature adjusted toabout 700 F. To the bath of lead, a calculated quantity of cuprouschloride, CuzCl-z, equivalent to 1.2 pounds copper per ton of lead isadded. The temperature is gradually raised, the cuprous chloride meltingto a fluid liquid at about 800 F.; and at 850 F., a reaction sets upbetween the lead and the CuzClz according to the following equation:

The bath is mixed with a mechanical mixer of suitable design to aid inthe reaction, the whole operation requiring only a few minutes to,complete. With proper mixing at the correct temperature the reaction isquantitative, the chloride slag analyzing not more than a few hundredthsof one percent of copper. The lead chloride produced by this reactionfloats to the top of the bath and as the kettle is allowed to cool to750 this slag freezes to a crust and is removed with the usual type ofskimmer leaving a. clean bath of copper bearing lead. The lead may bemolded out into suitable pigs and marketed,

The foregoing describes the preferred method of the invention in itssimplest form. For practical purposes, however, it has been found to bedesirable to modify the above-described operation with respect to thenature of the reagent employed, as, for example, by substituting themore common and less expensive salt, cupric chloride, C11C12.2H2O.Otherwise, the procedure followed is substantially the same as thatdescribed, and the resultant products are identical. To the bath ofmolten lead at 700 F., a calculated quantity of this reagent equivalentto 1.2 pounds of copper per ton of lead is added. In this case thereaction proceeds as follows:

A further modification of the procedure, and one which is preferred foreconomic reasons, involves the use of a reagent comprising a mixture ofchemical equivalent proportions of hydrated cupric sulphate, CllSO4.5H2Oand sodium chloride, NaCl. A suitable reagent may be prepared bymechanically mixing together the finely pulverized salts in the properproportions. This reagent is added to the bath of metal in amountequivalent to 1.2 pounds of copper per ton of metal to be treated. Thereaction takes place according to the following equations:

The procedure followed in carrying out this modified method may besubstantially the same as when a copper chloride is employed. Owing tothe presence of the inactive constituent, NazSOr, the melting point ofthe mixture is somewhat increased and it has been found necessary toheat the bath to about 975 F. to insure the complete liquefaction of thereagent and terminate the reaction. The reagent employed in this methodis preferred because of its relative cheapness. The copper sulphaterepresents a cheaper form which can be used, for example, as a reagentfor dezincing desilverized lead.

In the specific examples given above, the

amount of copper has been specified as 1.2 pounds per ton of lead to betreated which is equivalent to the eutectic of copper in lead of .06%Cu. However, it is to be understood that the quantity of copperintroduced in this manner is not him ited to any specific amount, it maybe greater or less than this quantity depending on the results desired.

The method of the invention may be employed for incorporating copper inany suitable leadbearing product. Thus, the method of the invention maybe employed for incorporating copper in lead refined by the Parkesprocessor any other process, lead base alloys, lead recovered from scrapmaterials, such, for example, as scrap cable sheathing, scrap batteryplate metal, scrap Babbitt or type metals, or any other form of leadregardless of its source. Furthermore, it is to be understood that themethod of the invention as described herein and illustrated in theforegoing specific examples is not limited to the incorporation ofcopper in refined lead only. The reagent may be added to the lead at anypoint in the refining operation subsequent to desilverization, ifdesilverization is necessary, the difference being that where metals arepresent which are above lead in the electromotive series such as zinc ortin, chlorides of these metals will form in preference to lead. Forexample, if the copper chloride is added to desilverized unrefined leadwhich contains residual zinc, the product formed will be zinc chloriderather than lead chloride which forms when relatively pure refined leadis used. The copper is uniformly precipitated and is retained by thelead throughout any subsequent operation. The chloride slag produced bythis treatment is recovered, zinc and lead chlorides finding many usesin the trades.

I claim:

1. The method of forming an alloy comprising copper and lead whichcomprises subjecting a molten bath containing metallic lead to theaction of a copper salt other than a chloride and a metal chloridecapable of reacting with the copper salt to form a copper chloride.

2. The method of forming an alloy comprising copper and lead whichcomprises subjecting a molten bath containing metallic lead to theaction of a copper salt other than a chloride and a chloride of analkali metal.

3. The method of forming an alloy comprising copper and lead whichcomprises subjecting a molten bath containing metallic lead to theaction of a copper salt other than a chloride and a chloride of analkaline earth metal.

4. The method of forming an alloy comprising copper and lead whichcomprises subjecting a molten bath containing metallic lead to theaction of copper sulphate and a metal chloride capable of reacting withcopper sulphate to form a copper chloride.

5. The method of forming an alloy comprising copper and lead whichcomprises subjecting a molten bath containing metallic lead to theaction of copper sulphate and an alkali metal chloride.

6. The method of forming an alloy comprising 7 copper and lead whichcomprises subjecting a molten bath containing metallic lead to theaction of copper sulphate and an alkaline earth metal chloride.

7. The method of forming an alloy comprising copper and lead whichcomprises subjecting a molten bath containing metallic lead to theaction of copper sulphate and sodium chloride.

8. The method of forming an alloy comprising copper and lead whichcomprises adding copper chloride to a molten bath of metallic lead at atemperature of about 700 F., agitating the bath to mix the lead andcopper chloride, and heating the mixture to a temperature of about 850F.

9. The method of forming an alloy comprising copper and lead whichcomprises adding a reagent comprising a mixture of copper sulphate andsodium chloride to a molten bath of metallic lead at a temperature ofabout 700 F. agitating the bath to mix the lead and the reagent, and

heating the mixture to a temperature of about.

10. The method of forming an alloy comprisingcopper and lead whichcomprises forming a mixture comprising metallic lead, copper sulphateand sodium chloride, heating the mixture to a tempreature of about 975F., thereby to efiect the production of lead chloride and a molten metalbath having elemental copper dispersed therein, cooling the bath toeflect the solidification of lead chloride-bearing slag on the surfaceof the molten metal, and pouring the molten metal into suitable molds.

11. The method of forming an alloy comprising copper and lead whichcomprises forming a mixture comprising metallic lead, copper sulphateand sodium chloride, heating the mixture to a temperature of about 975F., thereby to effect the production of lead chloride and a molten metalbath having elemental copper dispersed therein, cooling the bath toeflect the solidification of lead chloride-bearing slag on the surfaceof the molten metal, and pouring the molten metal, into suitable molds,the amount of copper sulphate employed being equivalent to about 1.2pounds of copper per ton of metallic lead in the mixture, and the amountof sodium chloride employed being at least chemically equivalent to thecopper sulphate employed.

FERNANDO B. PE'I'ERMAN.

